Tk S. Hunt on Chemical Classifications. 



399 













distinction contradicts the supposition that the so-called clear 

 spots which so generally appear in the yolk in almost all animals, 

 particularly at the commencement of the fissn ration, are merely 

 the remains of the germinative vesicle. Still less can they be 

 traced to the germinative dot, since it is well known that they 

 are always clear and transparent, and as far as I know, no one 

 has found red spots in the spheres produced by fissuration. 



This supposition, that the clear spots are derived from the re- 

 mains of the germinative vesicle, is moreover opposed by th< 

 following fact, which was observed by me and several of my 

 friends in Boston, in the ovarian eggs of Sabella, viz. that the 

 clear spots appear before the disappearance of the germinative 

 vesicle, as is seen in figs. 15-17. The spots were very distinct, 



15. 



16. 



17. 







Ovarian eggs of Sabellm, magnified 40 timet 



and had the characteristic oily appearance which has induced 

 several observers to designate them by the name of oil-drops. 

 In one ovulum we saw no less than three such spots, besides the 

 germinative vesicle, (fig. 16.) With a higher power and a slight 

 pressure they kept their relative positions, and a careful compari- 

 son of their outlines with that of the germinative vesicle, con- 

 vinced me that they were not surrounded by a membrane. 



Art. XXXVI. — On some principles to be considered in Chemi- 

 cal Classifications ; by T. S. Hunt, Chemist to the Geological 

 Survey of Canada. 



Read before the American Association for the Promotion of Science, at the annual 



meeting, held at Philadelphia, Sept. 20th, lb 18. • 



The progress of chemical investigation has made known a vast 

 number of substances under the different names of M products of 

 substitution," copulates, ethers and amids, which may be gen- 

 erally described as formed by the combination of two other com- 

 pounds and the elimination of water or hydrochloric acid. In 



Fig. 15. Egg showing the germinative reside and one clear spot. 

 Fig. 16. Egg showing the germinative vesicle and three clear spots, 

 Pig. 17. The same egg compressed 





